Structures including passivated germanium

ABSTRACT

A method of passivating germanium that comprises providing a germanium material and carburizing the germanium material to form a germanium carbide material. The germanium carbide material may be formed by microwave plasma-enhanced chemical vapor deposition by exposing the germanium material to a microwave-generated plasma that is formed from a carbon-containing source gas and hydrogen. The source gas may be a carbon-containing gas selected from the group consisting of ethylene, acetylene, ethanol, a hydrocarbon gas having from one to ten carbon atoms per molecule, and mixtures thereof. The resulting germanium carbide material may be amorphous and hydrogenated. The germanium material may be carburized without forming a distinct boundary at an interface between the germanium material and the germanium carbide material. An intermediate semiconductor device structure and a semiconductor device structure, each of which comprises the germanium carbide material, are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 11/122,798,filed May 5, 2005, pending. The disclosure of the previously referencedU.S. patent application is hereby incorporated by reference in itsentirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a method of passivating germanium. Morespecifically, the present invention relates to a method of carburizinggermanium to form germanium carbide.

One significant reason for the wide use of silicon, rather thangermanium, as a semiconductor substrate is the ease with which siliconis passivated. The silicon oxidizes, producing silicon dioxide, which isa good electrical insulator and passivator. The silicon dioxide alsoacts as a barrier, preventing impurities from penetrating the siliconwithout affecting the properties of the silicon. Alloys of silicon andgermanium are used in high-speed bipolar transistor structureshigh-frequency wireless radio frequency (“RF”) circuits. In addition,alloys of silicon, carbide, and germanium are used in high-power,high-temperature semiconductor devices. However, in many applications,such as in high-speed devices, germanium is a more suitablesemiconductor substrate than silicon or silicon alloys because theelectron mobility of germanium is higher. Germanium also has a directtransition that is only slightly higher in energy than the indirect bandgap. As a consequence, germanium has a higher absorption coefficientthan silicon, making germanium desirable in many optoelectronic orphotovoltaic applications.

While germanium also forms a native oxide, germanium oxide is a poorinsulator, is soluble in water and other solvents typically used toprocess semiconductor devices, and is volatile at elevated temperaturestypically used to process the semiconductor devices. Therefore,germanium oxide is not a good passivator for a germanium surface. Asdisclosed in U.S. Pat. No. 4,589,006 to Hansen et al., a diode formedfrom a germanium substrate is passivated with a layer of hydrogenatedamorphous germanium or hydrogenated amorphous silicon. The layer isformed by sputtering the germanium or silicon in a low pressureatmosphere of hydrogen and a noble gas.

Hydrogenated amorphous silicon is a widely studied material. It has beendetermined that the band gap energy of the hydrogenated amorphoussilicon depends on the degree of short range order in the material. Theband gap energies of amorphous materials are not well defined or wellknown but are generally higher than those of corresponding crystallinematerials. For instance, the band gap of crystalline silicon is 1.2 eVbut that of amorphous silicon is up to 2.0 eV.

U.S. Pat. No. 6,794,255 to Forbes et al., which is commonly assigned tothe assignee of the present invention, discloses forming silicon carbideby carburizing silicon. The resulting silicon carbide is preferablyamorphous. The silicon is carburized using microwave plasma-enhancedchemical vapor deposition (“MPECVD”). The silicon carbide is used as aninsulating dielectric layer in a field effect transistor (“FET”).

Band diagrams for crystalline silicon and crystalline silicon carbideare shown in FIGS. 1 and 2, respectively. The band gap of crystallinesilicon is 1.2 eV, the electron affinity is 4.2 eV, and the electronbarrier energy is 3.3 eV while the band gap of crystalline siliconcarbide is 2.1 eV, the electron affinity is 3.7 eV, and the electronbarrier energy is 2.8 eV. In contrast, amorphous hydrogenated siliconcarbide deposited by very high frequency plasma-enhanced chemical vapordeposition has a band gap of up to 3.4 eV. As such, the amorphoushydrogenated silicon carbide has a greater band gap than that of thecrystalline silicon carbide (2.1 eV). The amorphous silicon carbidedeposited on silicon has been shown to have a low surface recombinationvelocity and provides good passivation on silicon.

Germanium carbide films have been deposited or grown by chemical vapordeposition (“CVD”), plasma assisted CVD, molecular beam epitaxy (“MBE”),glow-discharge decomposition, RF reactive sputtering, or electroncyclotron resonance (“ECR”) plasma processing. Electrical and opticalproperties of the resulting films depend on the process of preparing thegermanium carbide films and the processing conditions that are used.Booth et al., “The Optical and Structural Properties of CVD GermaniumCarbide,” J. de Physique, 42(C-4) 1033-1036 (1981) discloses forminggermanium carbide films by CVD. The germanium carbide films havepolycrystalline germanium clusters distributed in a Ge_(y)C_(z) materialand, therefore, are neither crystalline nor amorphous. As disclosed inChen et al., “Electrical Properties of Si_(1-x-y)Ge_(x)C_(y) andGe_(1-y)C_(y) Alloys,” Journal of Electronic Materials, 26(12):1371-1375(1997), Ge_(1-y)C_(y) alloys that are rich in germanium are deposited onn-type silicon substrates by MBE. The Ge_(1-y)C_(y) alloys have improvedcrystalline quality and reduced surface roughness compared to puregermanium. Tyczkowski et al., “Electronic Band Structure of InsulatingHydrogenated Carbon-Germanium Films,” Journal of Applied Physics,86(8):4412-418 (1999) discloses forming hydrogenated carbon-germaniumfilms by plasma assisted CVD from tetramethylgermanium in a RF glowdischarge. After annealing, the hydrogenated carbon-germanium films havea band gap energy as high as 7.1 eV and an electron affinity of 1.2 eV.

Amorphous, hydrogenated germanium carbide has been deposited by avariety of techniques. U.S. Pat. No. 4,735,699 to Wort et al., Liu etal., “Structure and Properties of Germanium Carbide Films Prepared by RFReactive Sputtering in Ar/CH₄,” Jpn. J. Appl. Phys., 36:3625-3628(1997), Yu et al., “Asymmetric Electron Spin Resonance Signals inHydrogenated Amorphous Germanium Carbide Films,” Phys. Stat. Sol. B,172(1):K1-K5 (1992), Shinar et al., “An IR, Optical, andElectron-Spin-Resonance Study of As-deposited and Annealeda-Ge_(1-x)C_(x):H Prepared by RF Sputtering in Ar/H₂/CH₃H₈,” J. Appl.Phys., 62(3):808-812 (1987), M. Kumru, “A Comparison of the Optical, IR,Electron Spin Resonance and Conductivity Properties of a-Ge_(1-x)C_(x):Hwith a-Ge:H and a-Ge Thin Films Prepared by R.F. Sputtering,” Thin SolidFilms, 198:75-84 (1991), and Kelly et al., “Application of GermaniumCarbide in Durable Multilayer IR Coatings,” SPIE Vol. 1275 HardMaterials in Optics, (1990) disclose forming amorphous, hydrogenatedgermanium carbide films on silicon and glass substrates by RF reactivesputtering. The amorphous, hydrogenated germanium carbide films areformed from a germanium target using mixtures of argon and methane or aninert gas and a halocarbon gas. The resulting films are smooth,featureless, and have an amorphous structure. Increasing the carboncontent in the amorphous, hydrogenated germanium carbide films increasedthe hardness of the films. The atomic ratio (Ge/C) of the amorphous,hydrogenated germanium carbide films decreased by increasing the gasflow ratio.

Microcrystalline germanium carbide alloys are disclosed in Herrold etal., “Growth and Properties of Microcrystalline Germanium-CarbideAlloys,” Mat. Res. Soc. Symp. Proc., 557:561-566 (1999). Themicrocrystalline germanium carbide alloys are formed at low temperatures(300° C. to 400° C.) on glass, stainless steel, or crystalline siliconsubstrates by a reactive hydrogen plasma beam deposition technique. Themicrocrystalline germanium carbide alloys are grown using an ECRreactor. Up to 3% carbon is incorporated into the microcrystallinegermanium carbide alloys. The microcrystalline germanium carbide alloyshave a high degree of crystallinity and a grain size on the order of afew tens of nm. The best crystallinity is obtained on conductingsubstrates, indicating the importance of hydrogen ion bombardment inpromoting crystallinity. The defect density was low at the tested carboncontent. In Herrold et al., “Growth and Properties of MicrocrystallineGermanium-Carbide Alloys Grown using Electron Cyclotron Resonance PlasmaProcessing,” Journal of Non-Crystalline Solids, 270:255-259 (2000),higher temperatures (350° C. to 400° C.) are used to grow themicrocrystalline germanium-carbide alloys with hydrogen dilution and ionbombardment. The microcrystalline germanium-carbide alloys have up to 2%carbon incorporation. Optical absorption curves of the microcrystallinegermanium-carbide alloys parallel that of crystalline germanium. Inaddition, the microcrystalline germanium-carbide alloys have increasedband gaps with increasing carbon incorporation. At comparable band gaps,the absorption coefficient of the microcrystalline germanium-carbidealloys is larger than that of crystalline silicon. Microcrystallinehydrogenated germanium carbide films formed by RF reactive sputtering orECR plasma processing have a low carbon concentration, such as 4%.Therefore, the microcrystalline hydrogenated germanium carbide filmshave a band gap energy that is close to that of silicon (1.2 eV).

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a method of passivating germanium thatcomprises providing a germanium material and carburizing at least aportion of the germanium material to form a germanium carbide layer. Thegermanium carbide layer may be amorphous. The germanium material may bea germanium layer on a substrate or a germanium substrate. The germaniumcarbide layer may be formed by MPECVD by exposing the germanium materialto a micro-generated plasma that is formed from a source gas andhydrogen. The source gas may be a carbon-containing gas selected fromthe group consisting of ethylene, acetylene, ethanol, a hydrocarbon gashaving from one to ten carbon atoms per molecule, and mixtures thereof.In one exemplary embodiment, the source gas may be methane.

The germanium material may be carburized without forming a perceptibleor distinct boundary at an interface between the germanium material andthe germanium carbide layer. The germanium carbide layer may have aninitial thickness that lies within a range of from approximately 10 Å toapproximately 500 Å. The thickness of the germanium carbide layer may beincreased to lie within a range of from approximately 50 Å toapproximately 5000 Å by radio frequency reactive sputtering or electroncyclotron resonance plasma processing.

The present invention also relates to an intermediate semiconductordevice structure that comprises a germanium material and a germaniumcarbide material in contact with at least a portion of the germaniummaterial. The germanium material may be a germanium substrate or asubstrate comprising at least one other material, such as, for example,another semiconductor material having a germanium material on a surfacethereof. The germanium carbide material may be amorphous and maycomprise approximately equal amounts of germanium and carbon. Theintermediate semiconductor device structure may be substantially free ofa grain boundary in that an interface between the germanium carbidematerial and the germanium material is substantially free of a distinctor perceptible boundary.

The present invention also relates to a semiconductor device structure,such as a field effect transistor, that comprises a germanium material,a germanium carbide material in contact with at least a portion of thegermanium material, and integrated circuitry on a surface of asemiconductor device structure. The germanium material comprises agermanium substrate or a substrate that comprises at least one othermaterial and has a germanium material on a surface thereof. Thesemiconductor device may be substantially free of a grain boundarybetween the germanium material and the germanium carbide material. Forinstance, an interface between the germanium carbide material and thegermanium material is substantially free of a distinct boundary. Thegermanium carbide material may be amorphous germanium carbide and mayhave a thickness within a range of from approximately 10 Å toapproximately 500 Å.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming that which is regarded as the present invention,the advantages of this invention may be more readily ascertained fromthe following description of the invention when read in conjunction withthe accompanying drawings in which:

FIG. 1 is a band diagram for silicon;

FIG. 2 is a band diagram for silicon carbide;

FIGS. 3 and 4 are cross-sectional views of a germanium material and agermanium carbide layer formed on the germanium material;

FIG. 5 is a band diagram for germanium;

FIG. 6 is a band diagram for germanium carbide;

FIG. 7 shows band gap energies and electron affinities of siliconcarbide and germanium carbide;

FIG. 8 is a band diagram for germanium carbide on a germanium substrate;and

FIG. 9 is a cross-sectional view of an embodiment of an intermediatesemiconductor device structure of an n-channel FET that includes agermanium carbide layer as a passivation layer.

DETAILED DESCRIPTION OF THE INVENTION

A method of passivating a germanium material by carburizing thegermanium material is disclosed. As used herein, the terms“carburizing,” “carburization,” “carburized,” or other forms thereofrefer to incorporating carbon into at least a portion of the germaniummaterial, such as a surface region thereof. The germanium material maybe present on a semiconductor device that includes other layersincluding, by way of example only, integrated circuits that have beenpreviously fabricated thereupon. Forming the layers or integratedcircuits on the semiconductor device is known in the art and, therefore,is not described in detail herein. The germanium material may be asubstrate formed solely of germanium, a germanium layer on a morerobust, insulative carrier substrate, or a germanium layer on asubstrate that includes another semiconductor material. Germaniumsubstrates in the form of wafers are known in the art and arecommercially available in a variety of nominal diameters, such as3-inch, 4-inch, 8-inch, and 10-inch diameters. The germanium substrateemployed in the present invention may be undoped or may be doped withimpurities, as known in the art, to form n+ or p+ doped regions.Alternatively, the germanium material may be a layer of germanium(undoped or doped) that is present on a carrier substrate or a substratethat includes another semiconductor material. As used herein, the phrase“semiconductor substrate” refers to a conventional substrate or otherbulk substrate. Thus, the term “bulk substrate” as used herein includesnot only germanium wafers, germanium layers on an insulative substrate,and silicon wafers, but also silicon on insulator (“SOI”) substrates,such as silicon on glass (“SOG”) substrates, silicon on sapphire (“SOS”)substrates, epitaxial layers of silicon on a base semiconductorfoundation, and other semiconductor materials, such assilicon-germanium, gallium arsenide, or indium phosphide. For the sakeof example only, the semiconductor substrate may be a silicon substrateupon which the germanium layer is formed. The germanium layer may beformed on the semiconductor substrate by conventional techniques, suchas by CVD or ultrahigh vacuum CVD.

As shown in FIGS. 3 and 4 of the drawings (not drawn to scale),germanium material 2 may be carburized by MPECVD, forming a germaniumcarbide (“Ge_(x)C_(1-x):H”, where 0<x<1) layer 4 on a surface of thegermanium material 2. The germanium carbide layer 4 formed in this waymay be amorphous. Amorphous germanium carbide, rather than crystallinegermanium carbide, is preferred because grain boundaries may be presentin the crystalline germanium carbide. The crystalline germanium carbidemay also lead to charge trapping and diffusion of impurities. MPECVDutilizes a plasma that is produced by an electromagnetic field atmicrowave frequency. The resulting plasma-chemical reactions mayincorporate carbon into the germanium material 2, forming the germaniumcarbide layer 4. The germanium material 2 may be carburized in a MPECVDsystem. MPECVD systems are known in the art and are commerciallyavailable from numerous sources, such as from Applied Materials (SantaClara, Calif.) or Wavemat Inc. (Plymouth, Mich.). As such, MPECVDsystems are not described in detail herein. For the sake of exampleonly, the MPECVD system may be an Applied Materials single wafer systemmodel 5000, which is available from Applied Materials (Santa Clara,Calif.).

Before forming the germanium carbide layer 4, the semiconductor devicehaving the germanium material 2 may be cleaned or degreased to removegermanium oxide and other impurities present on its surface. To removethe impurities, the germanium material 2 may be etched with an etchsolution, such as a mixture of nitric acid and hydrofluoric acid,followed by quenching with methanol. Since germanium oxide is soluble inwater, the semiconductor device may also be rinsed with deionized waterto remove any germanium oxide that may be present on the germaniummaterial 2.

After cleaning, the semiconductor device may be placed in a reactorchamber of the MPECVD system, which is initially maintained at a lowtemperature, such as approximately 300° C. However, this initialtemperature may vary, depending on the dimensions of the germaniumsubstrate or the germanium layer. The reactor chamber may be initiallyevacuated to a pressure on the order of approximately 10⁻⁴ mTorr orapproximately 10⁻⁵ mTorr. To carburize the germanium material 2, thetemperature in the MPECVD system may be quickly increased and thepressure may be increased to less than or equal to approximately 2 Torr.As described below, the temperature and pressure changes produce amicrowave-generated plasma 6 to which the semiconductor device may beexposed. During the carburization, the MPECVD system may be maintainedat a temperature that ranges from approximately 800° C. to approximately1200° C., such as approximately 1000° C. Within this range, a highertemperature may be used when a relatively faster rate of forming thegermanium carbide layer 4 is desired, while a low temperature within therange may be used to achieve a relatively slower rate of formation.

The microwave-generated plasma 6 may be produced by introducing hydrogenand a source gas into the MPECVD system and exposing the hydrogen andsource gas to energy having a frequency within the microwave range, suchas energy having a wavelength that ranges from approximately 1 mm toapproximately 30 cm (from approximately 1×10⁹ Hz to approximately 1×10¹¹Hz). The source gas may be a carbon-containing gas, such as ethylene,acetylene, ethanol, a hydrocarbon gas having from one to ten carbonatoms per molecule, or mixtures thereof. The hydrocarbon gas mayinclude, but is not limited to, methane, ethane, propane, butane, etc.,or mixtures thereof. A rate of forming the germanium carbide layer 4 maybe affected by relative amounts of the source gas and the hydrogen usedin the MPECVD system. The greater the amount of source gas relative tothe amount of hydrogen, the faster the rate at which the germaniumcarbide layer 4 may be formed. Therefore, to form the germanium carbidelayer 4 at a relatively faster rate, a larger amount of the source gasmay be used relative to the amount of hydrogen. For instance, a highhydrogen dilution ratio may be used, such as on the order of 50:1.

The amount of source gas relative to the amount of hydrogen may alsoaffect the carbon content of the resulting germanium carbide layer 4.Therefore, by adjusting the amount of the source gas that is used, theamount of carbon incorporated into the germanium material 2 may becontrolled. The resulting germanium carbide layer 4 may range from beinggermanium rich (carbon poor) to carbon rich (germanium poor). Forinstance, the germanium carbide layer 4 may be Ge_(0.9)C_(0.1):H,Ge_(0.1)C_(0.9):H, or a material having a germanium and carbon contentthat falls in between Ge_(0.9)C_(0.1):H and Ge_(0.1)C_(0.9):H. Sinceelectrical and optical properties of the semiconductor device aredetermined by the amount of carbon in the germanium carbide layer 4,properties of the germanium carbide layer 4 may be tailored byincorporating a desired amount of carbon into the germanium carbidelayer 4. For instance, the band gap, electron affinity, or electronbarrier energy of the germanium carbide layer 4 may depend on the carboncontent of the germanium carbide layer 4. By increasing the amount ofcarbon in the germanium carbide layer 4, the band gap of the materialmay be increased and the electron affinity may be decreased. In oneembodiment, the germanium carbide layer 4 includes substantially equalamounts of germanium and carbon, i.e. x=0.5 in Ge_(x)C_(1-x):H.

A flow rate of the hydrogen and the source gas may also be adjusted tocontrol the amount of carbon incorporated into the germanium material 2.For instance, each of the hydrogen and the source gas may be introducedinto the MPECVD system at a flow rate that ranges from approximately 100standard cubic centimeters per minute (“sccm”) to approximately 1000sccm. To increase the carbon content in the germanium carbide layer 4, arelatively higher flow rate of the source gas to hydrogen within thisrange may be used.

The frequency of energy used to carburize the germanium material 2 maydepend on the dimensions of the germanium material 2 that is used. Forthe sake of example only, if the germanium material 2 is an 8-inch to10-inch germanium wafer, a microwave power of approximately 1,000 wattsmay be used. However, if the substrate or layer of germanium material 2is smaller, such as a 3-inch to 4-inch germanium wafer, a lowermicrowave power may be used, such as a power that ranges fromapproximately 250 watts to approximately 300 watts.

To carburize the germanium material 2, the semiconductor device havingthe germanium material 2 may be immersed in the microwave-generatedplasma 6. For instance, the semiconductor device may be immersedapproximately 0.5 cm into the microwave-generated plasma 6. Upon contactwith the microwave-generated plasma 6 for a sufficient amount of time,carbon may be incorporated into the germanium material 2, forming thegermanium carbide layer 4. The amount of time needed to form thegermanium carbide layer 4 may depend on a desired thickness of thegermanium carbide layer 4 that is ultimately to be formed. The thicknessof the germanium carbide layer 4 deposited by MPECVD may lie within arange of from approximately 10 Å to approximately 500 Å. The germaniumcarbide layer 4 having a thickness of approximately 10 Å may bedeposited in approximately one minute, while the germanium carbide layer4 having a thickness of approximately 500 Å may be deposited inapproximately one hour. Since the formation of the germanium carbidelayer 4 is a diffusion-limited process, a germanium carbide layer 4having a thickness at the high end of this range may require a longertime and a higher temperature to produce. The carbon may besubstantially uniformly incorporated into the germanium material 2. Assuch, no carbon gradient may be present in the germanium carbide layer4.

The germanium carbide layer 4 formed by the method of the presentinvention may be used to passivate a surface of the germanium material2, preventing impurities or dopants from penetrating into the underlyinggermanium material 2 and providing mechanical protection and electricalinsulation. The germanium carbide layer 4 is equivalent in performanceas a surface passivation to silicon dioxide grown on a siliconsubstrate. The germanium carbide layer 4 may passivate the underlyinggermanium material 2 without negatively affecting the optical andelectrical properties of the germanium material 2 and withoutintroducing mechanical strain into the germanium material 2. As such,the passivated, germanium material 2 may be used in a wide variety ofsemiconductor devices including, but not limited to, transistors(bipolar or FET) or optoelectronic devices, such as photodetectors,light emitters, infrared emitters, or photodiodes. FETs are used inprogrammable logic arrays (“PLAs”) or memory devices, such as inerasable programmable read only memory (“EPROM”), electrically erasableprogrammable read only memory (“EEPROM”), electronically alterableprogrammable read only memory (“EAPROM”), dynamic random access memory(“DRAM”), synchronous dynamic random access memory (“SDRAM”), SyncLinkdynamic random access memory (“SLDRAM”), RAMBUS dynamic random accessmemory (“RDRAM”), or flash memory devices. FETs are used as both accesstransistors and as memory elements in flash memory devices. Thegermanium carbide layer 4 may also function as an insulating, ordielectric, layer in the semiconductor device.

The germanium carbide layer 4 may provide good passivation of thegermanium material 2. Without being tied to a particular theory, it isbelieved that using MPECVD to form the germanium carbide layer 4 enableselectron bonds to continue across an interface between the germaniummaterial 2 and the germanium carbide layer 4 as the germanium carbidelayer 4 is formed. As such, substantially no grain boundary formsbetween the germanium material 2 and the resulting germanium carbidelayer 4. Therefore, no perceptible or distinct boundary forms at theinterface between the germanium material 2 and the germanium carbidelayer 4. In contrast, when germanium carbide is formed by a conventionaltechnique, such as by RF reactive sputtering or ECR plasma processing, aperceptible boundary forms at the interface between the underlyingmaterial and the germanium carbide layer. Since RF reactive sputteringand ECR plasma processing are deposition techniques, a distinct layer ofgermanium carbide is formed over the underlying layer. In other words,electron bonds do not form across the interface between the underlyinglayer and the germanium carbide layer, producing the boundary betweenthe two layers and resulting in a relatively weak bond between the two.

The band gap energies and electron affinities of germanium and germaniumcarbide are shown in FIGS. 5 and 6, respectively. The band gap energy ofgermanium is 0.67 eV and the electron affinity is 4.0 eV. The band gapenergy of germanium carbide ranges from 1.2 eV to 7.1 eV and theelectron affinity ranges from 1.2 eV to 3.8 eV. Possible band gapenergies and electron affinities of the germanium carbide are shown inFIG. 7. For comparison, band gap energies and electron affinities ofamorphous Ge_(x)C_(y):H produced by plasma assisted CVD, as described inTyczkowski et al., and microcrystalline Ge_(x)C_(y):H produced by ECR,as described in Herrold et al. (both of which are described above), arealso shown. FIG. 8 shows the band gap energy and electron affinity of agermanium carbide layer on a germanium substrate. The germanium carbidelayer on a germanium substrate may have an electron barrier energy of upto approximately 2.8 eV. As such, a germanium carbide layer formed byMPECVD may be suitable for passivating a germanium substrate or a layerof germanium material. Forming a germanium carbide layer by MPECVD mayalso result in a lower risk of producing undesirable microcrystallineinclusions. In addition, the resulting germanium carbide layer may havea lower surface state density than germanium carbide formed byconventional deposition techniques. Growth of the amorphous germaniumcarbide layer may enable completion of electronic bonds across theinterface between the germanium material 2 and the germanium carbidelayer 4.

Since forming the germanium carbide layer 4 by MPECVD, as illustrated inFIG. 4, is a slow process, conventional techniques may be used toincrease the initial thickness of the germanium carbide layer 4 formedby MPECVD. The thickness of the germanium carbide layer 4 may be furtherincreased, if desired, to achieve complete passivation of the germaniummaterial 2. The thickness of the initial germanium carbide layer 4 maybe increased by depositing amorphous germanium carbide by a conventionaltechnique, such as by RF reactive sputtering or ECR plasma processing. Atotal thickness of the resulting germanium carbide layer may lie withina range of from approximately 50 Å to approximately 5000 Å.Alternatively, another amorphous dielectric material, such as amorphoussilicon oxide, may be formed on the germanium carbide layer 4 toincrease its thickness. However, if only a relatively thin germaniumcarbide layer 4 is desired, the entire thickness of the germaniumcarbide layer 4 may be formed by MPECVD.

As previously mentioned, the germanium carbide layer 4 may be present ina semiconductor device structure, such as an FET, as a passivation layerfor a germanium material 2. An intermediate semiconductor devicestructure 8 of an n-channel FET is shown in FIG. 9. The methods andintermediate structures described herein do not form a complete processflow for manufacturing the semiconductor device. However, the remainderof the process flow is known to a person of ordinary skill in the art.Accordingly, only the process acts and semiconductor structuresnecessary to understand the present invention are described herein. Theintermediate semiconductor device structure 8 may include a sourceregion 10, a drain region 12, and a gate region 14. The source region 10and the drain region 12 may be fabricated by conventional techniques,such as by forming regions of highly doped (n⁺) regions in a lightlydoped (p⁻) germanium substrate 2′. Alternatively, the source region 10and the drain region 12 may be fabricated in a semiconductor substrate,such as a silicon substrate, having a germanium layer on its topsurface. The source region 10 and the drain region 12 may be separatedby a predetermined length in which a channel region 16 is formed. Thegate region 14 may be formed by conventional techniques fromconventional materials. A conductive layer 18, formed from polysiliconor a metal, may be formed over the gate region 14. For instance, theconductive layer 18 may be formed from polycrystalline silicon that ishighly doped and annealed to increase its conductivity. The gate region14, the conductive layer 18, and subsequently formed, overlying layersmay be etched, as known in the art, to produce the n-channel FET. Thesubsequently formed, overlying layers may be formed from insulatingmaterials, as known in the art, to produce the semiconductor devicestructure.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims.

1. An intermediate semiconductor device structure, comprising: agermanium material and an amorphous germanium carbide material incontact with at least a portion of the germanium material, wherein theamorphous germanium carbide material is carburized germanium with theformula Ge_(x)C_(1-x):H, wherein x is greater than zero and less than 1.2. The intermediate semiconductor device structure of claim 1, whereinthe germanium material comprises a germanium substrate or a substratecomprising at least one other material and having a germanium materialon a surface thereof.
 3. The intermediate semiconductor device structureof claim 1, wherein the substrate comprising at least one other materialis selected from the group consisting of a silicon wafer, a silicon oninsulator substrate, a silicon on glass substrate, a silicon on sapphiresubstrate, an epitaxial layer of silicon on a base semiconductorfoundation, a silicon-germanium substrate, a gallium arsenide substrate,and an indium phosphide substrate.
 4. The intermediate semiconductordevice structure of claim 1, wherein the amorphous germanium carbidematerial is hydrogenated.
 5. The intermediate semiconductor devicestructure of claim 1, wherein the amorphous germanium carbide materialcomprises approximately equal amounts of germanium and carbon.
 6. Theintermediate semiconductor device structure of claim 1, wherein theintermediate semiconductor device structure is substantially free of agrain boundary between the germanium material and the amorphousgermanium carbide material.
 7. The intermediate semiconductor devicestructure of claim 1, wherein an interface between the amorphousgermanium carbide material and the germanium material is substantiallyfree of a distinct boundary.
 8. The intermediate semiconductor devicestructure of claim 1, wherein the germanium carbide material has athickness within a range of from approximately 10 Å to approximately 500Å.
 9. A semiconductor device structure, comprising: a germaniummaterial; a germanium carbide material in contact with at least aportion of the germanium material, wherein the germanium carbidematerial is carburized germanium material with the formulaGe_(x)C_(1-x):H, wherein x is greater than zero and less than 1; and atleast one integrated circuit on a surface of a semiconductor devicestructure.
 10. The semiconductor device structure of claim 9, whereinthe germanium material comprises a germanium substrate or a substratecomprising at least one other material and having a germanium materialon a surface thereof.
 11. The semiconductor device structure of claim 9,wherein the substrate comprising at least one other material and havinga germanium material on a surface thereof is selected from the groupconsisting of a silicon wafer, a silicon on insulator substrate, asilicon on glass substrate, a silicon on sapphire substrate, anepitaxial layer of silicon on a base semiconductor foundation, asilicon-germanium substrate, a gallium arsenide substrate, and an indiumphosphide substrate.
 12. The semiconductor device structure of claim 9,wherein the semiconductor device structure is substantially free of agrain boundary between the germanium material and the germanium carbidematerial.
 13. The semiconductor device structure of claim 9, wherein aninterface between the germanium carbide material and the germaniummaterial is substantially free of a distinct boundary.
 14. Thesemiconductor device structure of claim 9, wherein the germanium carbidematerial is amorphous germanium carbide.
 15. The semiconductor devicestructure of claim 9, wherein the germanium carbide material has athickness within a range of from approximately 10 Å to approximately 500Å.
 16. The semiconductor device structure of claim 9, wherein thesemiconductor device structure comprises a field effect transistor. 17.An intermediate semiconductor device structure, comprising: a germaniummaterial and a germanium carbide material in contact with at least aportion of the germanium material, wherein the germanium carbidematerial is carburized germanium material with the formulaGe_(x)C_(1-x):H, wherein x is greater than zero and less than
 1. 18. Anintermediate semiconductor device structure, comprising: a germaniummaterial and a passivated surface thereof in contact with at least aportion of the germanium material, wherein the passivated surface of thegermanium material is carburized germanium material with the formulaGe_(x)C_(1-x):H, wherein x is greater than zero and less than 1.